The mesocortical areas of the cerebral hemisphere in the primate constitute a heterogeneous collection of cortical types linked historically to the limbic system by virtue of their strong reciprocal connections with the anterior and dorsal thalamus. Recently, however neuroanatomical studies have shown that, in addition to these connections, mesocortical areas also have strong reciprocal connections with a host of neocortical association areas thought to mediate complex or higher-order behavior. Additionally, several mesocortical areas are the target of direct dopaminergic projections from the mesencephalon. Combined with the fact that mesocortical entorhinal axons sprout and reinnervate a contralaterally deafferented dentate gyrus, these findings have led to a renewed interest in these phylogenetically old, yet progressive areas of the prime brain. Clearly, mesocortical areas communicate with most subdivisions of the brain and seem to play a crucial intermediary role in many aspects of behavior. However, convinced as we all might be of the latter, little is known about vast regions of the mesocortices, particularly primates. Consistent with the principal investigator's past research activities, the proposed research seeks to elucidate the following in Old World monkeys: (1) the efferent connections of mesocortical areas; (2) the afferent connections of mesocortical areas; (3) the distribution of dopaminergic afferents to mesocortical areas; and (4) the plasticity of mesocortical afferents as evidenced by reinnervation within the lateral nucleus of the amygdala. Modern experimental neuroanatomical methods including autoradiography, horseradish peroxidase, and histofluorescenc will be utilized to investigate these problems.